Wellbores are formed in subterranean earth formations for many purposes including, for example, oil and gas extraction and geothermal energy extraction. Many tools are used in the formation and completion of wellbores in subterranean earth formations. For example, earth-boring drill bits such as rotary drill bits including, for example, so-called “fixed cutter” drill bits, “roller cone” drill bits, and “impregnated diamond” drill bits are often used to drill a wellbore into an earth formation. Coring or core bits, eccentric bits, and bi-center bits are additional types of rotary drill bits that may be used in the formation and completion of wellbores. Other earth-boring tools may be used to enlarge the diameter of a wellbore previously drilled with a drill bit. Such tools include, for example, so-called “reamers” and “under-reamers.” Other tools may be used in the completion of wellbores including, for example, milling tools or “mills,” which may be used to form an opening in a casing or liner section that has been provided within a previously drilled wellbore. As used herein, the term “earth-boring tools” means and includes any tool and components thereof that may be used in the formation and completion of a wellbore in an earth formation, including those tools mentioned above.
Earth-boring tools are subjected to extreme forces during use. For example, earth-boring rotary drill bits may be subjected to high longitudinal forces (the so-called “weight-on-bit” (WOB)), as well as to high torques. The materials from which earth-boring tools are fabricated must be capable of withstanding such mechanical forces. Furthermore, earth-boring rotary drill bits may be subjected to abrasion and erosion during use. The term “abrasion” refers to three-body wear mechanism that includes two surfaces of solid materials sliding past one another with solid particulate material therebetween, such as may occur when a surface of a drill bit slides past an adjacent surface of an earth formation with detritus or particulate material therebetween during a drilling operation. The term “erosion” refers to a two-body wear mechanism that occurs when solid particulate material, a fluid, or a fluid carrying solid particulate material impinges on a solid surface, such as may occur when drilling fluid is pumped through and around a drill bit during a drilling operation. The materials from which earth-boring drill bits are fabricated must also be capable of withstanding the abrasive and erosive conditions experienced within the wellbore during a drilling operation.
The bodies of earth-boring tools may be relatively large structures that may have relatively tight dimensional tolerance requirements. As a result, the methods used to fabricate such bodies of earth-boring tools must be capable of producing relatively large structures that meet the relatively tight dimensional tolerance requirements. As the materials from which the earth-boring tools must be fabricated must be resistant to abrasion and erosion, the materials may not be easily machined using conventional turning, milling, and drilling techniques. Therefore, the number of manufacturing techniques that may be used to successfully fabricate such bodies of earth-boring tools is limited. Furthermore, it may be difficult or impossible to form a body of an earth-boring tool from certain composite materials using certain techniques. For example, it may be difficult to fabricate bit bodies for earth-boring rotary drill bits comprising certain compositions of particle-matrix composite materials using conventional infiltration fabrication techniques, in which a bed of hard particles is infiltrated with molten matrix material, which is subsequently allowed to cool and solidify.
As a result of these and other material limitations and manufacturing technique limitations, earth-boring tools may be fabricated using less than optimum materials or they may be fabricated using techniques that are not economically feasible for large scale production.